Cytron Technical Forum

Hello there, i wonder anyone here can help me how to make this 'Fading' effect for my LED sign? Currently i manage to make blinking led which not proper for my project. Hope the 'master' here can give me some idea what type of product that i can use.

At this time, i'm using 555 timer, capasitor, and some other component which not able to fade more then 1 LED. Thnxx in advance for your help yaa....

hi,

Pulse width modulation(PWM.

if u want to make it automatic fade in certain time, it can be done using any microcontroller which has the PWM module.

yonghui is right, you need to use PWM. However, usually a midrange PIC will have only one/two PWM(s). Each PWM can be used to control one LED. How many LED do you want to control?

If you need more PWM, you can:
1. write software to generate PWM using Timer and assign any I/O pins of the PIC as the outputs.
2. get a better PIC which has more PWM. Usually it comes in surface mount package and is more expensive.
3. use multi-PWM chip like this one. But you will still need a microcontroller to send command to it using serial communication.

Thnxx for your reply. Currently my signage having between 12 to 30 LED's which contains different color of led. Now, i also try by using 7 steps controller but its not working like what i wanted. Its should be an automatic fading with time limit. So, can you recommend to me your product that i can use in my project? Sorry in advance coz i'm totally '0' knowledge in this field. Just like when i started my 1st my DIY CNC Machine.

I hope you can list the parts number and the price as well ya. Hope its within my budget. Thanxx again for your help.

hi,

12 to 30 LED need to be controlled independently ?

the LED are normal 5mm LED or other high power type. how much current consumption of each LED u will like to biased? current will determine the brightness of the LED.



yh

Thnxx yonghui. The led is 5mm which super bright type. Range between 2volt and 3.3volt at 20ma. What it mean by "controlled independently"? Ok lets make its simple for me that so blur about your technical term. Just say this way:
I have a sets of LED's( orange) sets in series, 4led in 1 string(1set). And another sets will be blue led in series 3led in 1string(1set). So, just say i want to have 2sets of orange(8led's) and 2 sets of Blue(6led's).

Ok..the next step, i just on the switch and the led will start blink in fade in and out effect between this 2 color just say 3 or 4 sec alternate. Should i say randomly? Haa...haa..sorry for the long romantic story.. TQ for your kind respond in advance yaa...

Aiseyy... still no reply

If you need to control a row of LEDs, you might need a better transistor on it. Probably a FET or some current driver. As I do not have much knowledge of power electronics, you might need to search a bit more info about FET and current drivers for multiple LEDs.

PWM can be done with a microcontroller or a 555 timer. Use a cheap PIC12F or the Attiny series for all that fun.

Opamps work too. Here is one example:http://circuit-diagram.blogspot.com/2011/03/onoff-led-fade-effect-circuit-by-op-amp.html

Btw, can you draw a picture of what you need to do with the LEDs? In that way we can assist you better.

Thnxx Brian for your kind replies. Actually i have tried many of the led fading that been search form the internet. I have follow thier diagram,but seems it not working. For single led,yes its work. But when tried to run 2 led, its failed. For your perusal i attach herewith my project that i working on.

http://www.facebook.com/photo.php?fbid=109890672435632&set=a.102286166529416.4797.100002440988495&type=1&theater

Blinking is not suitable for my project, that's why i need ' fading effect '. thanxx again for your help.

I remember saw some article or product post about this.....actually if you use PWM to drive MOSFET in high frequency, it will not blink, it will fade (brightness will change). I think you can try looking for TLC5940, is a 16 channels PWM output chip.